Geological Survey Water-Supply Paper 1475-J Ground Water in the Wupatki and Sunset Crater National Monuments, Coconino County, Arizona

The main source of ground water in the area is from that part of the precipitation which percolates down through the permeable rocks into the zone of saturation in the Coconino sandstone and the upper sandy part of the Supai formation. Perched zones of saturation occur where the downward percolation is retarded by impermeable material. Most of the ground water in the Coconino sandstone in this area is probably from precipitation received in the region south and southwest beyond the mapped area (pl. 20). Recharge to the alluvial deposits is aided by intermittent streams carrying small quantities of runoff from San Francisco Mountain.

Ground-water movement in the Coconino sandstone, as indicated by the water-table gradient, is to the northeast (fig. 45). The altitude of the water table in the Sunset Crater area is estimated to he about 5,000 feet, based on the projection of the slope of the water table as determined from Wells (A-22-10)3ad, (A-23-10)1bb, and (A-23-10)13dc (table 1). Data from deep wells in the vicinity of the Wupatki National Monument indicate that the water table is at an altitude of about 4,075 feet near Wupatki Ruin and about 4,100 feet near Citadel Ruin.

Only a few wells have been drilled in the volcanic rocks; therefore, the amount of water these rocks contain is not known. However, they are not likely to yield large quantities of ground water because they are above the regional water table. Small supplies of perched water occur in the Moenkopi formation and Quaternary alluvium, and some may be present in the volcanic rocks. A few springs discharge from the base of basalt flows west and south of the area.

The southwestern part of the area is most favorable for recharge of water to the underground reservoir in the Coconino sandstone, owing to the presence of highly permeable volcanic rocks and the large amount of annual precipitation. In the northern part of the area, the total amount of recharge through the exposed surfaces of the Kaibab limestone and volcanic rocks is limited because of the low annual precipitation. Some recharge may occur from the Little Colorado River to permeable beds in the Moenkopi formation and possibly through them to older formations. The recharge areas that contribute to perched ground-water bodies, such as those at Wupatki and Heiser Springs, are probably small and do not extend far from the areas of discharge.

Perched ground water from aquifers in the Moenkopi formation and volcanic rocks in the Wupatki-Sunset Crater area is discharged from springs and seeps, which occur at a few locations in the Wupatki area and along the Little Colorado River. Data from Wupatki and Heiser Springs indicate that the total spring discharge is not directly related to total precipitation (table 3). However, there is a correlation between the winter snowfall and the flow of the springs, as shown in plate 21. Summer rainfall seems not to affect spring discharge. The combined yield from Wupatki and Heiser Springs ranges from less than 1 to about 3 gpm.

TABLE 3.—Comparison of spring discharge and precipitation, Wupatki-Sunset Crater area, Coconino County, Ariz.
[Assumed recharge area: Heiser Spring, 8-1/2 acres; Wupatki Spring, 3-1/2 acres]

PLATE 21.—DISCHARGE OF HEISER AND WUPATKI SPRINGS COMPARED WITH WATER CONTENT OF SNOW ON GROUND AND PRECIPITION, WUPATKI NATIONAL MONUMENT, COCONINO COUNTY, ARIZONA. (click on image for an enlargement in a new window)

Ground water in the Coconino sandstone is pumped from a few deep wells that are used for stock and domestic purposes. Some of these wells yield as much as 15 gpm, but larger yields probably could be obtained by a deeper penetration of the saturated zone of the aquifer and by installing pumps of larger capacity. About 20 miles southwest of the Sunset Crater National Monument, a well in the Flagstaff well field that penetrated about 375 feet of saturated Coconino sandstone produces about 450 gpm.

The results of the field investigation indicated that adequate ground water was available in the Coconino sandstone for the needs of the headquarters area of the Wupatki National Monument. It was estimated that a well drilled to a depth of 800 to 900 feet would have a water level of 700 to 800 feet. Well (A-25-10)30bca was drilled for the Wupatki National Monument in the fall of 1958 on the basis of this information. Mr. Russell L. Mahan, superintendent, supplied the following information. The well was drilled to a total depth of 904 feet, through 10 feet of overburden, 95 feet of Moenkopi formation, 220 feet of Kaibab limestone, and 579 feet of Coconino sandstone. Water was tapped in the Coconino at a depth of 801 feet and rose 21 feet, reaching a static water level at 780 feet below land surface. The well was pumped for 24 hours at 50 gpm with a drawdown of 45 feet. The water level is reported to have returned to the static level 17 minutes after the pump was shut off. The chemical quality of the water is reported to be fair (table 4).

TABLE 4.—Chemical analyses of water from selected wells and springs, Wupatki-Sunset Crater area, Coconino County, Ariz.
[Analyses expressed in parts per million. Analyses by U.S. Geological Survey, except (A-26-10)35 as by U.S. Bureau of Indian Affairs]

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QUALITY OF WATER

The ground water within the Wupatki-Sunset Crater area contains moderate to large amounts of dissolved solids (table 4). The dissolved-solids content of the water from 3 sampled springs ranges from 448 to 1,030 ppm (parts per million); in the water from 7 sampled wells, the range is from about 136 to more than 1,500 ppm. Drinking water should contain less than 500 ppm of dissolved solids, but as much as 1,000 ppm is permissible for use on interstate carriers, according to U.S. Public Health Service standards (1946). Water containing more than the suggested limits of dissolved mineral matter has been used by many persons for long periods without ill effects.

The fluoride content of the water in Wupatki and Heiser Springs is greater than the 1.5 ppm maximum recommended by the U.S. Public Health Service, and the water is undesirable for drinking water for children because it is likely to cause mottling of teeth. The fluoride content of water from wells in the area is less than the recommended maximum.

Chemical analysis of a sample of water taken from well (A-25-10)30bca at Wupatki headquarters during a bailing test showed a total of 1,030 ppm of dissolved solids and a hardness of 427 ppm. The fluoride content is only 0.8 ppm, which is not objectionable in supplies for domestic consumption.